Widdowson U.S. Pat. No. 3,525,234 shows a receiver containing a thermostatic expansion valve and a suction throttling valve, each of the valves being in integral subassembly form and mountable in the receiver. This patent is assigned to General Motors Corporation and, not surprisingly, is used extensively in General Motors Corporation air-conditioned automobiles.
The thermostatic expansion valve capsule shown in the Widdowson patent provides an O-ring seal preventing axial flow along the operating pin of the expansion valve, thus keeping the very cold refrigerant from the underside of the diaphragm where it could, in effect, take away control from the head chamber above the diaphragm. The patent expansion valve is somewhat costly to manufacture.